1. Field
Embodiments may relate to a light emitting device, a light emitting device package, and/or a lighting system.
2. Background
A light emitting device (LED) may include a p-n junction diode having a characteristic of converting electric energy into light energy. The p-n junction diode may be formed by combining group III-V elements of a periodic table. The LED may represent various colors by adjusting a compositional ratio of compound semiconductors.
The LED may be classified as a lateral type LED or a vertical type LED based on position of an electrode.
The electrode of the vertical type LED may be divided into a p type electrode and an n type electrode. The p type electrode may supply holes and represent low mobility due to a great effective mass of the holes so that the p type electrode may be formed over the whole area of a p-GaN layer.
The n type electrode may be positioned at a light exit surface so that the n type electrode is on a part of an N—GaN surface. Although the n type electrode is partially formed on the N—GaN surface, electrons may freely move in the n-GaN layer so that current may normally flow without causing serious problem.
However, light quantity or electric characteristics, such as operational voltage, may vary depending on area or shape of the n type electrode. For this reason, the n type electrode of the vertical type LED may employ a structure capable of maximizing wall-plug efficiency by taking light quantity and operational voltage characteristics into consideration.
The operational voltage characteristic may be improved as the area of the n type electrode is increased. However, light quantity may be reduced as the area of the n type electrode increases because the n type electrode has limited reflectivity.
Even if the n type electrode is an ideal reflective layer having reflectivity of 100%, light reflected from the n type electrode may be introduced again into the device and absorbed in the device so that the light quantity may be reduced. Thus, it may be desirable to develop the n type electrode capable of improving the light quantity while satisfying the operational voltage characteristic.